new block_until_locked() method in InMemory and Persistent
Merge branch 'develop' of /software/vertres/git/origin/vr-pipe into develop
Debuggable warn() and throw() no longer call log() to avoid complication with VRPipe::Persistent::InMemory->log()
InMemory->locked() has new by_me option; also has new maintain_lock() method to auto-refresh a lock
No more Living.pm (soon to be replaced with InMemory methods)
we now use Scalar::Util
flush the redis test database when a test starts, so tests do not have to manually delete redis keys
added a _clear_maintenance_watchers() method for use by forked child processes
Living.pm has been removed along with Persistent->lock_row(), and now all locking and monitoring is done with InMemory lock-related methods; this means Job no longer has a heartbeat so schema change